The present invention relates to a method for determining calibration data for a grain-loss sensor on a combine harvester.
Grain losses during the harvesting operation of a combine harvester refer to the grains of the picked-up crop stream which were either not initially effectively threshed out of the straw or, despite having been threshed out by the threshing mechanism or by the cleaning assembly of the combine harvester, were not further conveyed into the grain tank, which is actually desired. Instead, such grain loss grains are left on the field by the combine harvester, as is the threshed-out straw. These grain losses, which should be kept low if possible, depend on the ground speed and the operating settings of the threshing mechanism, in particular, of the combine harvester and on ambient conditions such as the condition of the crop and of the field, e.g., in terms of moisture and crop density. Invariable and optimal settings for the threshing mechanism therefore do not exist for all basic conditions; instead, these must be adjusted according to the aforementioned ambient conditions and the ground speed in order to reduce or minimize the grain losses.
At the same time, economic requirements regularly exist with respect to a maximum grain loss, which must not be exceeded during the harvesting of a field and which can be indicated as a proportion of all grains or by another metric. It is often additionally economically useful or required, while observing the maximum grain loss, to simultaneously minimize the duration of harvesting, which would be possible, e.g., by increasing the ground speed, or to reduce the energy consumption of the threshing mechanism, wherein these two requirements have certain conflicting goals with the grain losses. The driver of the combine harvester therefore regularly strives to operate the combine harvester slightly below the specified grain-loss limit.
The determination of the present grain losses, which is important for such an adjustment, during the harvesting operation has proven to be difficult so far. On the one hand, it is known from the prior art that the driver of the combine harvester or a helper on the field between the straw and chaff left behind by the combine harvester qualitatively determines the density or quantity of the loss grains, which also are left behind. Such conventional method, however, is both complicated and inaccurate, and adjusting the settings of the combine harvester when a new measurement is carried out is time-consuming, in particular. This principle is only slightly improved by the use of control pans for receiving loss grains, which are either set down by the combine harvester at certain times or are manually placed by a helper for capturing the grain loss.
Grain-loss sensors disposed on the combine harvester also are known from the prior art, which are disposed, e.g., in the region of a straw walker rack of the threshing mechanism and are intended to determine the grain losses on the basis of the detected impact behavior of falling grains. The concept of grain losses is intended to mean, here and in the following, either an absolute value of grain losses, e.g., expressed in grain volume or grain mass per unit of field area, or a relative amount based on another variable.
A problem associated with these grain-loss sensors is that it is difficult to establish a relation between the values measured by the grain-loss sensor and the actual grain losses. The reason is that the relation between the values measured by the grain-loss sensor, which are referred to here and in the following as sensor grain-loss values and which represent the measurement signal per se, which is generated by the grain-loss sensor, and the actual grain losses likewise depends very heavily on the overall volume of the grain stream and on the aforementioned ambient conditions. Hence, it is difficult to calibrate the grain-loss sensors in order to determine the actual grain losses.
Patent document DE 198 20 819 C2, describes the possibility of calibrating the grain-loss sensors by evaluating the aforementioned control pans, although the highly inaccurate assignment of the measured values of the grain-loss sensors to the evaluation of the control pans limits the precision of the calibration. In addition, the method is highly time-consuming.